Phosphate (Pi) and its anhydrides constitute
major nodes in metabolism. Thus, plant performance depends directly on
Pi nutrition. Inadequate Pi availability in the rhizosphere is a common
challenge to plants, which activate metabolic and developmental
responses to maximize Pi usage and acquisition. The sensory mechanisms
that monitor environmental Pi and transmit the nutritional signal to
adjust root development have increasingly come into focus. Recent
transcriptomic analyses and genetic approaches have highlighted complex
antagonistic interactions between external Pi and Fe bioavailability and
have implicated the stem cell niche as a target of Pi sensing to
regulate root meristem activity.

In eukaryotes, E3 ubiquitin ligases (E3s) mediate the ubiquitylation of
proteins that are destined for degradation by the ubiquitin-proteasome
system. In SKP1/CDC53/F-box protein (SCF)-type E3 complexes, the
interchangeable F-box protein confers specificity to the E3 ligase
through direct physical interactions with the degradation substrate. The
vast majority of the approximately 700 F-box proteins from the plant
model organism Arabidopsis thaliana remain to be characterized. Here, we
investigate the previously uncharacterized and evolutionarily conserved
Arabidopsis F-box protein 7 (AtFBP7), which is encoded by a unique gene
in Arabidopsis (At1g21760). Several apparent fbp7 loss-of-function
alleles do not have an obvious phenotype. AtFBP7 is ubiquitously
expressed and its expression is induced after cold and heat stress. When
following up on a reported co-purification of the eukaryotic elongation
factor-2 (eEF-2) with YLR097c, the apparent budding yeast orthologue of
AtFBP7, we discovered a general defect in protein biosynthesis after
cold and heat stress in fbp7 mutants. Thus, our findings suggest that
AtFBP7 is required for protein synthesis during temperature stress.

Auxin regulates a host of plant developmental and physiological processes, including embryogenesis, vascular differentiation, organogenesis, tropic growth, and root and shoot architecture. Genetic and biochemical studies carried out over the past decade have revealed that much of this regulation involves the SCFTIR1/AFB-mediated proteolysis of the Aux/IAA family of transcriptional regulators. With the recent finding that the TRANSPORT INHIBITOR RESPONSE1 (TIR1)/AUXIN SIGNALING F-BOX (AFB) proteins also function as auxin receptors, a potentially complete, and surprisingly simple, signaling pathway from perception to transcriptional response is now before us. However, understanding how this seemingly simple pathway controls the myriad of specific auxin responses remains a daunting challenge, and compelling evidence exists for SCFTIR1/AFB-independent auxin signaling pathways.